Automatic chain or belt tensioning mechanism



Sept. 21, 1943. H. e. KELLER AUTOMATIC CHAIN OR BELT TENSIONING MECHANISM Filed Aug. 17 4 Sheets-Sheet 1 wo /wan Sept. 21, 1943. H. G. KELLER AUTOMATIC- CHAIN OR BELT TENSIONING MECHANISM Filed Aug. 17, 1942 4 Sheets-Sheet 2 Sept. 3- H. G. KEILLER 2,329,911

AUTOMATIC CHAIN OR BELT TENSIONING MECHANISM Filed Aug. 17, 1942 4 Sheets-Shet s j e'zary 611 1101 s jt. 21, 1943. H, ELLER v 2,329,911

AUTOMATIC CHAIN OR BELT TENSIONING MECHANISM Filed Aug. 17, 1942 4Sheets-Sheet 4 Patented Sept. 21, 1943 AUTOMATIC CHAIN OR BELT TENSIONING I MECHANISM Henry G. KellergGlenside, Pa., assignor. to.Link- Belt 'Company,.a. corporation of Illinois Application August 17, 1942, Serial No. 455,096

This. invention relates to new and useful im-.

provementsin mechanismfor automatically maintaining a desired amount of tension on the driving chains or belts of variable speed transmission gearing. 1 v In my patent numbered 2,266,687, issued December 16,.1941, I hav disclosed and claimed mechanisms which are capable of maintainin at all times-a uniform maximum tension on the driving chains or belts of variable speed trans: mission gearing. The mechanisms of said pat ent Operate on the principle of constantly applying one force tothe chain or belt in such a manner. as to produce a sag therein and of constantly applying a second force to the chain or belt in such a manner as to reduce, but not eliminate, theamount of sag. These two opposed forces will apply the maximum tension to the driving chain or belt only when they are neatly balanced, orin a state of equilibrium. As the driving chain or belt develops increments of wear or stretch, it becomes longer. This increase in length throws the opposed forces out of bal-j ance. Because the opposed forces will always seek a state of balance or equilibrium whenever that condition does not exist, they will imme diately reestablish that condition and themaximum tension will again be applied. 'As a result of extensive use of mechanisms embodying the above noted principle, it has'b'een determined thatalthough the degree of maximum tension applied to the driving chain or belt ofja given transmission gearing unit ismain tained uniform at all times, the degrees of maximum tension applied to the driving chains or beltsof difierent gearing unitsare not exactly the same. This difference result from normal manufacturing tolerances which are allowed for the commercial productionof such gearing units,

and particularly the springs of such units which are employed for creating th oppositely acting forces. 'The degreeof maximum tension maintained for each unitwill depend upon just what relativepositions or settings are assumed bythe force delivering instrumentalities when the opmission units maybe held withinentirely satisfactory limits. v j

Theautomatic driving chain orbelt tensionin'g' mechanism embodying this invention is an improvement over the mechanisms of my afore said patent because it operateson the principle of .constantly applyingfonly a sag producing force tothe chain or belt to maintain the'desired degree of maximum-tension, and, whenanincrement of wear or stretch develops which will produce such an elongation of'the-drivingchain or belt as will lower 'the'degreeof tension provided by 'the sag producing force below the" de= siredma'ximum, of momentarily applying a force to the driving chain or belt in such a manner as to eliminate the increase in sag that-resulted from such {increment of wear or stretch. -Ihe extent or period of application *of the sag eliminating force is automatically controlledso that itwill do no more than eliminate the aforesaid increase in sag.

- It will be apparent, therefore, that the maintaining of a uniform maximum tension with this improved apparatus is not dependent upon-the balancing of two forces and the position or set ting assumed by the force applying instrumentalities whensaidforces are balanced. Instead, it is only necessary to employ a force developing means which will be capable of producing the "desired degree of maximum tension on the driving chain or belt by creating a sag therein and employ a second force developing-means, having a'powe'r factor superiorto that of the sag developing force toany desired degree, 'for eliminating-any additional sag that develops in the driving chain or belt.

It is the primary object of this invention to provide an automatic 'tensioning mechanism for chains or belts of variable speed transmission gearing which will apply and maintain a tension within comparatively narrow limits regardless of posed springs assume their state of balance or equilibrium. However; by exercising a reason able amount of care in selecting and matching the springs that are assembled in each transmission gearing unit, and by regulating the setting or position assumed by the force applying instrumentalities when the opposed force producing springsare in a stateof balance or equilibrium; the. differences between the degrees of maximum tension maintained in different transload or speed conditions.

-A- further important object of the invention is to provide automatic tensioning mechanism which will apply a suitable tension to a driving chain or belt by constantly" applying a sag producing force thereto and which will maintain said'tension within comparatively narrow limits at all times by applying a'sag eliminatingforce to the driving chain or belt onlywhen'the depth of the sag therein exceeds that which exists-When the maximum tension is appliedr a Other objects anda dvant'ages of the invention will be apparent durin'g the course of'thefollo'wing description. a

Figure 4 is a detail sectional view taken online 4-4 of Fig. 1,

Figure 5 is a detail vertical sectional view of'aportion of the tensioning mechanism embodying this invention, and V Figure 6 is a detail plan view of the reset crank of said mechanism. a

In the drawings, wherein. forthe purpose of illustration is shown the preferred embodiment of this invention, and first particularly'referring to Figs. 1, 2, and 3, there is disclosed. a, variable speed transmission gearing unit which includes the housing I, having'abase portion 8,.andhaving opposite side and top openings. Figs. 2. and 3 disclose the side openingsas being closedby side plates 9 and I0. ..Figs. 1 and 3 disclose the t'op opening of the casing as being closed by a removable inspection cover plate I; l. i

Fig. 2 discloses the two side plates 9 and. Ill as having formed therein the bearing openings l2 in which suitable bearings [3 are mounted These bearings are adapted to supp ort the. constant speed driver shaft [4 and the variable speed driven shaft 15. It will be seen that each oneof these two shafts has one end projecting. out wardly of the housing through one of its bearing openings t2. These projecting shaft portionsare adapted to have mounted thereon suitable power transmitting devices and are provided with key ways I 6 for that purpose. Bearing caps t!- of annular formation are positioned inthe bearing openings I 2 through which the ends of the shafts l4 and- I5 project. The remaining two bearing openings l2 are closed by solid bearing caps t8; All of the caps I! and I8 are threadedl-y connected to the side plates 9 and: l so that. they may be removed whenever it becomes necessary to repair or replace'the shaft bearings l3-. Both of the shafts M and are provided with splined portions I 9 for having axially slidably mounted thereon the conical wheels or cones 2.0. Each pair of these wheels forms a. V-pulley for its respective shaft. Each wheel 20 is -provide'd with a conical contact surface or face 2| and a relatively long hub portion 20a. These hub1 portions allow for axial sliding movement of" the wheels 20 toward and away from each other 'whilebeing drivingly connected to its shaftby means of the splines I9. A flexible transmission member 22 is illustrated in Figs. Land 2' as-being trained over the expansible and contractible V'- pulleys which are formed by the pairsof wheels 20. The wheels of the twopulleys are illustrated as'being positioned with their respective contact surfaces 2| uniformly spaced so that both pulleys will have the same effective diameter. Itiss to be understood, however, that the wheels, maybe spacedv different distances in the two pulleys so as to have different effective diametersa. When the pulley of the driver shaft M has the larger effective diameter, the speed of rotation of the driven shaft l5 will be reater than the speed of rotation of the driver shaft. When the relative l'il It will be understood; however, that the faces 2| "of' the wheels 20 may he formed as disclosed n the G. J-. Abbott Patent No. 1,637,402, issued Asugust 2;. 1927,. while the flexible transmission member 22 may be formed in the manner shown in the G. J. Abbott Patent No. 1,814,883, issued July 13,1931. Smooth and toothed faced pulley wheels. with appropriately constructed flexible transmission members-are well known in the art and for that reason it is believed to be unnecessary to disclose indetailboth of these types of gearings. Therefore, in the specificationand claims the expression a contractible and expansible V-puiley' is'intended' to embrace wheels having either smooth or toothed contact surfaces or. faces while the expression 'a flexible trans mission member is intended to embrace either belts or chains of appropriate construction for use on these two difierent types of V-pulleys. It was pointed out above that the wheels" M are axially slidablysplined' onthe shafts 19st! that they may be expanded and contracted to vary the effective diameters of the pulleys formed by the same. As one pulley is caused to expand, the other pulley will be correspondingly contracted; 'The efi'ective diameter of a pulley is increased by forcing its opposed Wheels 2!! toward each other- Whenthe effective diameter is to be reduced, the wheels ZIT are permitted to move away from each other. The mechanism employed. for forcing. the wheels of one pulley toward each. other simultaneously operates. to permit the wheels of the remaining pulley to expand or move away from each other. The diameters of the two pulleys, therefore, are increased. and decreased in proportion with each other.

Figs. 2, 3 and 4Ydisclose fulcrum blocks" zsana 24 which. are. adjustahly mounted; on the oppositely threadedportions' Z5 and 28 of an adjust ing. screw 'ZT Whicht is journal'ed in. bearing, en: largementsJZE. and 29 formed. on.,the side. plates 91 and Ill respectively. Adjusting. screw. 21. is are ranged in parallelism with and. between the driver shaft. [4' and. driven. shaft t5 screw threadedlportions. 25: and. 26 of the. ad.- justing. screw. are positioned so as. to arrange-the pivot. or fulcrum blocks 21 and 24. on opposite sides of. the two .V-pulleys. 3 illustrates each pivot or fulcrum block. as being, provided with. pivot. studs. 30 on which are'mounted. the operating levers 3t for pivotalv movements It will be seen; therefore. that each. one of the fulcrum blocks. 23 and 214 has. pivotally. mounted thereon, two controlling or. operating levers M Figs. 1 and 2 disclose each. pair of centrolling or operating. levers3l as-being; providedwitha pair of. spacing. and. bracing, members. 32. with these members. 3?. being. arranged on. opposite sides of their fulcrum blocks 23 and. 24.. Any suitable means may be employed for. attaching the. spacing and. bracing, members. 32 rigidly to the operating or controlling levers 31.

; Each pulley wheel hub 1211a has mounted there on a ball thrust bearing 33ywith one iaCe'BIb. gaging the back or outerface of its wheel.v A thrust yoke 34 bearsagainstthe.remaining race of each one of the. thrust bearings 33.:1These thrust yokesare provided with studs 35 that are arranged 'to 'be received in :suita'ble'openings. formed in the Controlling or'operating levers -3|; asf'is best illustrated in Figs. 1, 2fan'd 5. It will be seen from this arrangement that each one of=the pulley wheels 20 is backed up ibya ball thrust bearing 33 and a thrust'yoke34. whileeach one of the thrust yokes is connected to both of the operating or controlling levers 3| that are arranged on one side of the two V- pulleys Whenever the respective effective diameters of the two V-pulleys are to be changed relative to each other, it is necessary to pivot the control levers 3| about theirstuds '30. To accomplish this pivotal movement of the controlling or operating levers control blocks'36 are connected to ends of the levers 3| inthe-manne'r illustratedin Figs.'1 and 2. Suitable speed control mechanism, not illustrated in detail in these two figures, is provided for moving the control blocks 36 toward and away from each other. Reference may be made to my prior Patent No. 2,266,687 for a complete disclosure of this'control mechanism. i r The introductory portion of the specification points out that the desired tension is applied to the flexible transmission member 22 in accord ance with this invention by producing a predetermined amount of sag in 'the flexible transmission member and by employing additional mechanism for maintaining the depth of the sag within narrow limits. The sag is normallyproduced in the non-driving run of 'the flexible transmission member. It is pointed out in my prior patent that mechanism for "producing a sag in a flexible transmission member becomes less effective as the depth of the sag increases. For that reason, the sagp'roducing mechanism can only maintain the desired maximum'tension in the flexible transmission member when the depth of the sag is Withincertain vanes, These fcertain values, therefore, idetermine the normal amount of sag to be provided in the transmission member. When increments of wear or stretch develop in the flexible transmission member, the length of. the member increases and the depth of the sag naturally increases; Therefora'it is necessary to eliminate appreciable increase in the depth of sag as it develops to permit the sag producing mechanism to' maintain the flexible transmission member tensionedwithin the: desired limits. c I 1 The sag producing mechanism is best i1lustrated in Figs. 1, 2 and 3. It consists of a'pairof lever members 31 which are pivotally mounted on the shafts 38 that extend transversely of the housing for being journaled at their opposite ends in the side plates 9 and It. by means of the raised bearings 39. A transmissio-nmember engaging shoe do is connectedto the outer end of each lever member 3'! by means of a combined ivot and actuating pin 4|. Fig. 2 clearly illustrates one of the pins 4| as projecting laterally oi its lever 31. A bracing arm 42 extends from the lever 31 tosupport this projecting portion of the pin 4|. 7 .The function of this projection will be explained indetail at a laterpoint, Fig. 3 disclosesthe pins 4| for both of the shoes 40 as projecting laterally of the shoes. It will be expl nne a a a r, Wi iih FiRe Y 3 tion of travel ofth'eflexible transmission member 221only one of these pins 4| will be required to have its projecting portion perform an additional function. However, as thetransmission may be driven in either direction, the pins for both flexible transmission member engaging shoes 40 must be elongated in the manner illustrated.

It willbe seen by inspecting Figspl, 2 and 3 that the shoes engage both the active, or driving,and the inactive, or return,-runs of'th'e flex ible-transmission member 22 betweenthetwo V-" To apply the desired amountofforceto the levers 31 to produce a sag in thdnontd'riizing run of the flexible transmission 'member, tension springs-l2 are provided These springs are suit ably connected at their opposite ends tothe f le vers 3? adjacent their supporting s'hafts ,33; The sag is produced in the non-drivingrunof; the flexible transmission member as a result of the force developed by the springs li and delivered to both-runs of the transmission memberbythe shoes 40. The application'of pressure to the flex ible transmission member naturally tensions "this member. The tensio-n'will varyin intensity as the angle'formed by the sides'of thesag in the flexible transmission member variesf "The-ten sion produced by thespring loadedlevers 31 will decrease as-the included angle of the sidesofthe sag decreases, or as the depth'of the sag increases.

This reduction in tension results not onlyfr'orn the contraction of the springs dzbutalso as'a result of the decrease in the included angle formed by the sides of the sag For'the sag pro ducing mechanism to maintain the desired mast mum tension at all times therefore; the sagmust not be permitted to increase in depth beyond what has been determined to be a normal amount; i. e., the'depth at which the, force of the sag producing mechanism will be efiective to pro duce thedesired tension. i

The mechanism that i employed for eliminat in any sag which develops beyond theno'rma'l amount will now be described.- Figs. 2, 3 and 5 disclose the tension adjusting screw 2'! as having keyed on one end portion thereof the'worm gear 43. This worm gear meshes withtheworm- 44 that is slidably mounted on the resetshaft' '45 and is held against rotation with respect to this shaft by means of the key 46. A washer All bea-rs against the lower end of the worm M and isienf gaged by the upper end of the actuating spring 48 which is on the lower portion of the reset shaft 45. A stop sleet/e49 is fitted on there'set shaft within the actuating spring 'tfl andi sheld in' place by the pin 5% This step sleeve 59 is of proper length to engage the washer 4'! for limit} ing the degree or extent to Whichthe spring 48 may be compressed.

'The top wall la of the housing Tisprovided with an opening 5| to receive the removable mounting sleeve 52 which is heldin place by the headed screws 53. This mounting sleeve 52 acts as a bearing for the upper end o-fthe'reset shaft 45; A stop collar 54 i pinned to the reset shaft 65 and bears against the inner end of the sleeve 52 so as to prevent vertical movement of thereset shaft 45 relative to the sleeve 52 j reset crank 55 is slidably connectedto the actuating upper, projecting, squared end; portion 58 of the reset shaft 45. This reset crank is normally maintained iIrv contact with the upper face ol' the supporting sleeve 52 by means of the. lock spring 51'. This lock spring maintains the reset crank. 55 in a position where it will engage one or the other ofthe heads; of: the securing screws 53. 'l'hisens ementprevents rotatiom'of the reset. shaft-.45. Whenit-is desired tarota-te this shatt by mean ofthe'reset' crank. 55, the crank ismcvedupwardly to compresscthelock spring 51 and to free the reset crank 55: f-rom the-holding screws 53. s l

By inspecting Fig. 5,. it willv be seen that the worm 44 occupies a position where the actuating spring 48 is compressed almost toqthe maximum amount; that is tosay, the Washer 4'1 is; spaced only slightly from the adjacent emiof the stop sleeve 49. With the worm 44- occupyingthis-position and being prevented from rotating with respect tothe reset shaft 45: by means of thelkey 46= and with the reset crank 55' engaging one of the headedstop pins 53 so as toprevent rotation of the reset shaft 45, the force ofthe actuating spring 48 will tend to move theworm 44: upwardlv. Any upward movement t 1e' worm 44 will cause the same toact as a rack to rotate, the worm. gear 43 in the direction of the: arrow 55: Should the worm gear 43 be rotated by vertical movement of the worm 44', the-adjustment screw 21 would also be rotated. Rotation of the adjustment screw in the direction of the arrow 56 would bring about movement of the fulcrum blocks 23- and- 24 toward each other This approach movement or the fulcrum blocks would cause the controlling or actuating levers 3+ tobe moved toward each other for contracting the pairs of wheels of both of the V--pulleys=. Contracting of the pulleys would result in increasing their effective diameters and would bring. about elimination of sag in the non-driving run of the flexible transmission member 22.

Of course, vertical upward movement of the worm 44 is accomplished by the spring 48 and is accompanied by expansion of said spring. It is not desirable to permit the spring 48 to expand too much because the spring. must be able to; deliver a predetermined amount of force throughout its entire working range of expansion. The

stop collar 54, therefore, will function to limit the vertical upward movement of the worm 44 and the-expansion of the spring 48-.

When. the spring 48 has been expanded to its permissible limit, it becomes necessary to reset. or recompress' the spring. This is accomplished by lifting the reset crank 55 upwardly intothe position illustrated in dotted lines in Fig. 3, or into-a position Where it will clear the stop screws 53. When the reset crank 55 has been freed, itcan be turned in a clockwise direction for a right. hand thread, as viewed from above, for. rotating. the reset shaft 45; If we now consider that the worm gear 43 is held against rotation, the worm 44 will be caused to move downwardly by the rotation of the reset shaft 45. This downward movement of the worm can be continued until the washer 4! engages the upper. end of the stop, sleeve 49,. When the actuating spring. 48 has. been. compressed to the limit, the reset crank 5.5 is. released and the lock spring 51 will return the crank to the position illustrated in; full. lines in Figs. 3 and 5.

As the adjusting screw 21. is only intended to be rotated by the spring actuated or powered gear set 43-44 when. the sag in theflexible transmission member 22 exceeds the normal'depth or amount, it becomes necessary to provide means for holding: the. adjusting: screw 24' against rota..- tionwhen the normall amount; ofzsag is present in the flexible transmission member. This mg screwholding means: consists of a ratchet wheels. 58 which is illustrated in' Figs. 1-. to 4 inclusive: as: being keyed to the. end portion or the: ad justing screw 2"! that'is iournalhctin: thesideplate ill; Operatively' associated with. this ratchet wheel: 513 is: a: pawl: 5lrthaitis pivotally mounted on the pawl pim Ellar Figs. 35 and 4 clearliv' illustrate this pawlzpin as; being. suitably attached. to: the fulcrum block 24. A pawl return spring 8 l funca tions to: retain the pawl- 59 in its ratchet wheel holding. position and. to return: the pawl. to: such position. after it hasbeen; pivoted to release the ratchet whe'eh Operation of theadgiusting screw holding pawl 59 is accomplished by the doubleended control cam plate 62.. Fig. 4. clearly illustrates. this' con.- trolca-mplate as being .izournaled on the boss or projection 63 formed on the fulcrumv block. 241 A. snap ring 645 functions to retain this; double ended control: cam plate. 62 in; position on the 13055101 projectionzliiii Fig. 1 discloses the control-i cam plate. 62. as having an: arcuate slot-.35 formed therein to accommoda-te. the pawls pin 60 This slot. will permit the plate 62 to move relative to the pin 60. A pawl actuating or releasing. pin 66 is carried by the cam plates: and functions to trip or release the pawlwhen the control cam plate ismoved in a. counterclockwise direction, as viewed. in Fig. 1. A cam plate return spring 61 functions to normally urge the cam plate in aclockwise direction. as viewed in Fig. 1. Engagement of the pawl pin 60 with one. end of the: arcuate slot willlimit angular movement oi the cam plate oz by its return spring Bl.

It. will-be noted by particularly inspecting Fig. 1 that the control. camplate 62' has. oppositely directed. cam-surfaces i8.which are presented to the projecting end portionsoi the actuating pins 41 It will be. recalled that. these. pins also function as pivot pins for connecting. the. shoes 4! to the ends of the sag producing levers 31';

Fig.1 discloses the flexible. transmission memher 22 as. having the. normal depth or amount 01' sag provided in the non-driving run, or upper run, ofvthe same. When. this normal amount. of sag, exists, theactuat'ing. pin 4| ofthe shoe that produces the sag is spaced a. desired distance from the cam surface. 68; of the control cam plate, whichis presented to this pin 4|- As in.- crements of wear or, stretch. develop in the flexi ble transmission. member 22 andbring' about an elongation of this member, the actuating pin 4| oi the sag producing shoe 4H will be moved to ward. and finally into engagement with the cam surface 68;.

As soon as the sag exceeds the normal amount by a. predetermined value, the. actuating pin 41 brings about movement of the control cam plate 62' a sufiicient distance to cause its pawl release pin 53? to engage the. pawl 59 and pivot the latter to release the ratchet wheel 58. When this ratchet wheel is released; the spring. powered gear set 43-.44 will be. actuated and will effect rotation. of theactuating screw 21- Rotation of theactuating. screw willcause the fulcrum blocks 23' and 24 to be moved toward each other for moving the control or actuatmg levers 3| in the same direction; The final result will be that the opposedpairs of wheels 20; forrrn'ng'the two v pulleys will be moved. toward? each other to increase the efl'ectivedrameters of both pulleys:

operative when the depth of the sag has increased This increase in effective diameters will elim'- inate sagfrom the flexible transmission member 22. As the sag is eliminated,- the actuating pin 4|, of the sag producing shoe 40, will be moved. outwardly and will permit the return spring 61 to'move the control cam plate 62 in a clockwise direction; This movement of the camoplate 62 finally results in causing the pawl releasepin 66 to be moved out of engagement with the pawl 59 wherebythe spring 6| will return the pawl to its ratchet wheel holding position and further rotation of the actuating screw'zl bythe spring powered gear set 4344 will stop. o

It will be appreciated that the depth or amount of sag allowed the flexible transmission member 22 may be Very accurately controlled. This control is accomplished by thecontour of the cam surfaces 68, the normal positioningof theieflfective cam surface 68 with respect to the. efiective actuating pin 4| and by the normal spacing between the pawl release pin 66 and the portion of the pawl 59 which is engaged by said pin.

i It is to be-understood thatthe form of this invention herewith shown and described is to be taken as the preferred example ofthe same, and that various changes in the shape, size, and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described the invention, I claim: I 1. In variable speed transmissions of the parallel shaft type; a contractible and expansible V-pulley mounted on each shaft and each including a pair of relatively movable members having opposed conical contact surfaces, relatively movable control levers for the pairs of relatively movable members pivoted on opposite sides of said pulleys, a flexible transmission member trained over said pulleys for intimate contact with the same at their respective effective diameters, means for constantly applying force thereagainst to produce a sag therein andto increase the depth of the 'sag asslack develops in' the transmission member, means to move the pivots for said control members toward each other for simultaneously increasing the efiective diameters of both of said pulleys to reduce the amount of sag in the flexible transmission member, and means for'rendering said pivot moving means operative when the depth of the sag has increased a predetermined amount beyond normal and for,

rendering said pivot moving means inoperative when the sag hasbeen reduced tothe normal amountw- I V i 2. In a variable speed transmission of the parallel shaft type, a contractible and expansible V-pulley mounted on each shaft and' each includ-, ing a pair of relatively movable members having opposed conical contact surfaces, control members for the, pairs of relatively movable members supported by separate pivots'on opposite sides of said pulleys, a flexible transmission member trained-over said pulleys forintimate contact with the same attheir respective effective diameters, spring powered means engageable with the flexible transmission member for constantly applying force thereagainst to produce a sag therein and for increasing said sag as slack develops in the transmission member, spring powered means to move the separate pivots for the said control members toward each other for simultaneously increasing'the efiective diameters of both of said pulleysto reduce the amount of sag in the flexible transmission member, and

' means; for rendering saidpivot moving means a predeterminedamount' beyond normal and for rendering said pivot moving means inoperative whenithe 's'ag has been reduced to the-normal amount;

: -3.;In variable'speed, transmissions cfthe parallel "shaft :1 type, *a contractible and expansible Vepulley mounted on'each shaft; each of said pulleys including, a pair; oi-relatively movable members having opposed contact surfaces, con-. :trol members for the .pairs of relatively movable members pivoted onf'opposite sides -.of said pulleys, means. for adjusting said control members'about their; pivots to vary the eifective diameters ofsaid: pulleys in opposite directions; :a;;flexible transmission member trained over said pulleys for intimate contact withthexsame at their re-' spective, effective diameterspmeans engageable with the flexible,transmissiongmember for con stantly applying" force thereagainsti in sucha manneras to produce a sag therein and to provide the flexible transmission member with the desired-tension,:only when said transmission member hasagnormaliamount of sagxtherein, said means operatingto-increase the'depth of the-sag as slack: develops -in' the transmission member, means :to' move the pivots for the control mem bers towardreach" other for -'simultaneously iricreasing the" effective diameters "of both of said pulleys to, reducelthe amount of sag in the flex:-

ible transmission ymemben. andnmeans for ren-j f dering said" pivot moving means operative when the depth of the saghas increased apred'eterimined amount lbeyon'dnormal and for rendering said pivotv moving means inoperative whens-the sag hasibeen reduced to othe'n'ormal amount.

4. In-variable speed transmissions ofthe parallel shaft typeya contractible and expansible V-pulley mounted on each'shaft and each including a pair of relatively'movable members having opposed conical contact. surfaces, control levers, for the 'pairsiof-relatively movable mema .bers arranged on opposite sides'of the V'-pulley's,

a'fulcrum' block on each sid'eoof the 'V-pulleys for pivotallyrmountingsaid control levers, a flex ible transmission member trained over said pulleys-for intimate contact with the same at their respective efiective diameters, :mean'sw engageable with the;,flexibletransmission member" for constantlyv applyingi forcex th'ere'against :to produce 1a, sag therein, an adjustable "screw rotatable "to move-the: fulcrum blocks toward each; other for simultaneously increasing the eiiective diam' eters of both of said pulleyameans'to turn the adjusting1:screw to increase the effective diam etersofsaid pulleys so as to reduce the amount of sag in:the flexibletransinission member,- and means forrendering said adjusting screw turning-mean'soperative when the depth of the sag has increaseda, predetermined amount beyond normal and-for rendering'i'said adjusting screw has been turning 'means" inoperative when the sag reducedto the normal amount.

.. 5.; A; variable speed transmission comprising parallel driver anddriven shafts,= a contractible and'rexpansible \l-pulleylmounted on each shaft and :each pull'ey 'includinga pair of relatively movable members having opposed conical contact surfaces, control levers for the pairs of relatively movable members arranged on opposite sides of the v' pulleys, a fulcrum block on each side of the V-pulleys for pivotallymountingsaid control -levers,,means for adjusting the said con,- trol levers about their pivots to vary-the eifec fiv d amet o r ll v n PpQ t ir Q1-.

'having'opposed conicalcontact surfaces, control levers for the pairs of relatively movable members arranged on opposite sides of the V-pulleys, a fulcrum block on each side of. the V-pulleys for. pivotally mounting said control levers, a flexible transmission member trained over said pulleys for intimate contact with the same at their respective effective diameters,means engageable with the flexible transmission'rmember.for constantly applying force thereagainst to produce a sag therein, an adjustable screw rotatable to move the fulcrum blocks toward each other for simultaneously increasing the effective diameters of .both of said pulleys, means to turn the adjusting screw to increase the effective diameters of said pulleys so as to reduce the amount of sag in the flexible'transmission member, and means controlled by the operation of the'sag producing means for rendering said adjusting screwfturning means operative whenthe depth of the. sag has increased a predetermined amount beyond normaland for rendering said adjusting screw turning means inoperative when the sag has been reduced to the normal amount.

12; A variable. speed transmission comprising parallel driver and driven shafts, acontractible and expansible V-pulley mounted on each shaft and each pulley including a pair "of relatively movable members having opposed conical contact surfaces, control levers for the pairs of relatively ,movable' members arranged on opposite sides of the V-pulleys, a fulcrum block on each side of the V-pulleys for pivotallyfmounting said control levers, means for adjusting the said control levers about their pivots to vary the effective diameters of said pulleys in opposite. directions, a flexible transmission member trainedover said pulleys for intimate contact with the same at their respective effective diameters, spring powered means engageab-le'with the flexible transmission member vfor constantlyrapplying force thereagainst to produce a sag therein, an adjusting screw rotatable to move the fulcrum blocks toward each other for simultaneously increasing the effective diameters of both of said pulleys,- .spring powered means to turn the adjusting screw to increase the effective diameters of said pulleys so as to reduce'the amount of sa'g in the flexible transmission member, and means controlled by the operation of the sag-producing means-for rendering the adjusting screw :turning leans operative when the depth of the sag has increased a predetermined amount beyond normal and for rendering said adjusting screw turning means inoperative when thersag has been reduced to the normal amount;

13. In variable speed transmissions of the parallel shaft type, a contractible iand'expansible V-pulley'mounted Oneachshaft'and each including a pair'of relatively movable members having opposed conical contact surfaces, relatively movable control levers for the pairsflof relatively movable members pivoted on opposite"- sides" of said' pulleys, .a flexible transmission member trained over said pulleys for intimate contact with the same'at their respective effective diameters, means engageable withlthe flexible" transmission member for constantly applying force thereagainstto produce a sag therein and to :increase the depth of the sag as slack 'develops in the transmission member, means including a spring driven gear set to move the pivots for the said control membersv toward each otherf'or simultaneously increasing the effective diameters of both of said pulleys to'redu-ce the amount of sag in the flexible transmission'member',an'd means for renderingusaid pivot moving means operative when the depth of the sag has increased a predetermined amount beyond normal and for rendering said Ipivotmoving means inoperative when the sag'has been reduced to the normal amount. I

14. In variable speed transmissions of the parallelshafttype, a contractible and expansible v-pulley mounted on each shaftand' each including a pair'iof relatively movablemembe'rs havingopposed conical contact surfaces, relatively movable control levers for the pairs of relatively movable member's pivoted'on opposite sides of said pu1leys, a flexible transmission member trained over said pulleys for intimate contact with'the same at their respective efiective diam eters, means engageable with the flexible transmission member for constantly applying force therea'g'ainst-to produce a sag therein and to increasethe depth of thesag as slack develops in the transmission "member, means including a springpowered gear'set to movethe pivots for the said control members toward each other for 7 simultaneously increasing the effective diameters of both of said pulleys to reduce the amount of sagin the flexible transmission member, and I means controlled by the operation of the sag pr'o- 'ducing means for rendering said pivot movin means" operative when the depth of the sag has increased a predeterminedamount beyond normalandfor rendering said pivotmoving means inoperative when the sag has been reducedtothe normal amount. 9 9 a l5. In variable speedtransmissions of the parallel shaft type, a 'contractible and 'expansible V-pulley mounted on each shaft and each including a pair of relatively movable members having opposed conical contact surfaces, 'controllevers for Y the pairs of relatively movable members arranged on opposite sides of the V-pulleys,"a fulcrum block on each side of the V-pulleys for pivotally mounting said control levers, a flexible transmission member'trained over said pulleys for intimate contact with the same at their respective effective diameters, meansj engageable with the flexible transmission member for constantl applying force thereagainst toproduce a sag therein, an adjusting' screw rotatable'to move thejfulcrum blockstow'ard each other for simultaneously increasingly the effective diameters of both of said pulleys, a 'spring'driven'ge'ar set to turn the adjusting screw to increase the effective diameters of said pulleys so 'asto reduce the amount of sag in the flexible transmission memher, and means for rendering said adjusting screw turning means operative when the depth of the sag has increased a predetermined amount beyond normal and for'rendering'said adjusting screw turningm eans inoperative when the sag has been reducedto" the. normal amount.

l6. Invariable speed transmissions of the parallel shaft type, ja contractible and expansible V-pulley mounted'on each shaft and each in;-

cluding a pair of relatively movable members hava ing opposed conical contact surfaces, control 1evers'for the pairsiof relatively movable members arranged on opposite sides of the V-pulleys, a fulcrum block on each side of theV-pulle ys' for pivotally mounting said control levers, a flexible transmission member trained over said pulleysfor intimate contact 'witlrthe same at their respective effective diameters, means engageable with the flexible transmissionmember fo'r constantly 'applyin'g'force thereagainst to produce a sag therein-an adjusting screwrotatable to move the fulcrum blocks toward each other for simultaneously increasing the effective diametersof :both of said pulleys, a spring driven gear set to turn the adjusting screw to increase the effective diameters of said pulleys so as to reduce the amount of sag in the flexible transmission member, and means controlled by the operation of the sag producing means for rendering said adjusting crew turning means operative when the depth of the sag has increased a predetermined amount beyond normal and for rendering said adjusting screw turning means inoperative when the sag has been reduced to the normal amount.

17. In variable speed transmissions of the parallel shaft type, a contractible and expansible V-pulley mounted on "each shaft and each including :a pair of relatively movable members having opposed conical contact surfaces, a flexible transmission member trained over said pulleys for in- :timate contact with the same at their respective effective diameters, means to provide the flexible tiansmission member with the desired tension when pmduci-ng a normal amount of sag therein, means including .a spring driven gear set for simultaneously increasing the effective diameters of both .of saidpulleys to reduce the amount of sag therein, and means for rendering said sag reducing means operative when suflicient slack develops in the flexible transmission member to cause the depth of the sag to increase beyond said normal amount and (to render said sag reducing means inoperative when the sag has again been returned to said normal amount.

18. In variable speed transmissionsrof the parallel shaft type, a contractible and expansible V-pulley mounted on each shaft and each including a pair of relatively-movable .members having opposed conical contact surfaces, a flexi- .ble transmission member-trained over said pulleys for intimate contact with the same at their respective effective diameters, means to provide the flexible transmission member with the desired tension when producing the normal amount of sag in the flexible transmission member, means including a spring driven gear set for simultaneously increasing .the effective diameter of both of said pulleys to reduce the amount of sag in the transmission member, and means controlled by the .sag producing means .for rendering said sag reducing means operative when ,sufllcient slack develops in the flexible transmission member to cause the depth of the sag to increase beyond said normal amount and to render said sag reducing meansinoperative when the sag has again been returned to said .normal amount.

19. A variable speed transmission comprising parallel driver and driven shafts, a contractible and expansible V-pulley mounted on each shaft and each pulley including a pair of relatively movable members having opposed conical contact surfaces, control levers for the pairs of relatively movable members arranged on opposite sides of the V-pulleys, a fulcrum block .on .each side of the V-pulleys for .pivotally mounting said control levers, means for adjusting the said control levers about their ,pivots to vary the efiective diameters of said pulleys "in opposite directions, a flexible transmission member trained over said pulleys for intimate contact with the same at their respective effective diameters, spring powered means engageable with the flexible transmission member for constantly applying force thereagainst to produce a sag therein, :an adjusting screw rotatable to move the fulcrum blocks toward each other forsimultaneously increasing the effective diameters of both of said pulleys, spring powered means to turnthe adjusting screw to increase the effective diameters of said pulleys so a to reduce the amount of sag in the flexible transmission member, means for holding the adjusting screw from being turned by the spring powered means, and mean for rendering said screw holding means inoperative when the depth of the sag has increased a predetermined amount beyond normal and for rendering said screw holding means operative again when the'depth of thesag has been returned to normal,

20. In variable speed transmissions of the parallel shaft type which includes contractible and .expansible V-pulleys mounted on the shafts and a flexible transmission member trained over said pulleys, the improvement which comprises means for producing a sag in the flexible transmission member to tension said member, means for reducing the amount of sag in said member, and means controlled by operation of the sag producing means to render the sag reducing means operative when the depth of the sag has increased a predetermined amount beyond normal and to render the sag reducing means inoperative when the sag has been reduced to the normal amount.

21. In variable speed transmissions of the parallel shaft type which include contractible and expansible V-pulleys mounted on the shafts and flexible transmission members trained over said pulleys, the improvement which comprises spring poweredmeans for producing a sag in the flexible transmission member to tension said member, spring powered means for reducing the amount of sag in said member; and means controlled by operation of the sag producing means to render the sag reducing means operative when the depth of the sag has been increased a predetermined amount beyond normal :and to render the sag reducing means inoperative when the sag has been reduced to the normal amount.

22(In variablespeed transmissions of the parallel shaft type which include contractible and expansible V-pulleys mounted on the shafts and flexible transmission members trained over said pulleys, the improvement which comprises spring powered means for producing a sag in the flexi- -ble transmission member to tension said member, spring powered means for reducing the amount of sag insaid member, and a pawland ratchet mechanism controlled by operation of the. sag producing means to render the sag reducing means operative when the depth of the sag has increased a predetermined amount beyond normal and to render the sag reducing means inoperative when the sag has been reduced to the normal amount.

23. In variable speed transmissions of the parallel shaft type which include contractible and expansible V-pulleys mounted on the shafts and flexible transmissionmembers trained over said pulleys, the improvement which comprises means for producing a sag in the-flexible transmission member to tension said member, means for reducing the amount of sagin said member, and a pawl and ratchet mechanism controlled by operationof the sag producing means to render the sag reducing means operative when the depth of the sag has increased a predetermined amount beyond normal and to render the sag reducing means inoperative when the sag has been reduced to the normal amount.

24. In variable speed transmissions of the par allel shaft type which include contractible and expansible V-pulleys mounted on the shafts and flexible transmission members trained over said pulleys, the improvement which comprises spring powered means for producing a sag in the flexibl transmission member to tension said member, means including a spring driven gear set for reducing the amount of sag in said member, and means controlled by operation of the sag producing means to render the sag reducing means operative when the depth of the sag has increased a predetermined amount beyond normal and to render the sag reducing means inoperative when the sag has been reduced to the normal amount.

25. In variable speed transmissions of the parallel shaft type which include contractible and expansible V-pulleys mounted on the shafts and flexible transmission members trained over said pulleys, the improvementwhich comprises means for producing a sag in the flexible transmission member to tension said member, means including a spring driven gear set for reducing the amount of sag in said member, and means con-' to render the sag reducing means operative when the depth of the sag has increased a predetermined amount beyond normal and to render the sag reducing means inoperative when the sag has been reduced to the normal amount.

26. In variable speed transmissions of the parallel shaft type which include contractible and expansible V-pulleys mounted on the shafts and flexible transmission members trained over said pulleys, the improvement which comprises spring powered means for producing a sag in the flexible transmission member to tension said member, means including a spring driven gear set for reducing the amount of sag in said member, and

a pawl and ratchet mechanism controlled by op-' eration of the sag producing means to render the sag reducing means operative when the depth of the sag has increased a predetermined amount, beyond normal and to render the sag reducing means inoperative when the sag has been reduced to the normal amount.

HENRY G. KELLER.

trolled by operation of the sag producing means 

